The Rear Guard
A Rear Guard is essential to a force advancing in order to pick up the stragglers, to keep off marauders, and to prevent surprise by an energetic enemy who may detach a force for a surprise attack on the rear of the advancing column.
But its most important work is the protection of a retreating force, and this work will vary in difficulty with the freshness and enterprise of the enemy and the spirit and determination of the force that is being pursued. Generally speaking, Rear Guard fighting against an unexhausted enemy is the most difficult and most dangerous of all military enterprises. When a Rear Guard halts to fight it is being separated every minute from the Main Body, which is moving away from it, while every minute brings reinforcements to the enemy. The work requires great tactical skill, as it is the duty of the commander to delay pursuit by occupying positions from which he withdraws at the last moment, without becoming involved in a general engagement, from the meshes of which it may be necessary for the Main Body to return and extricate him. The work also requires great moral courage, as it is the duty of the commander to risk the loss of his force if by so doing he is adopting the only means of saving the Main Body.
STRENGTH.—The strength of the Rear Guard will depend upon the energy, strength, and closeness of the pursuit, the condition of the Main Body (and whether it is withdrawing voluntarily or upon compulsion after an unsuccessful engagement) and upon the nature of the country, but it will generally amount to not less than one-fifth or more than one-third of the whole force, and will be selected, as a rule, from those who have been least severely engaged.
COMPOSITION.—Its composition depends upon the work to be performed, and this calls for detachments of all arms of the land service, in addition to Aircraft, which can prevent surprise by reconnaissance over the hostile area and can harass the pursuing columns by day and by night by fire-action with Lewis guns and bombs. Mounted troops are required to extend the area watched and to prolong the resistance by reason of their superior mobility, in addition to their counter-action as cavalry. Artillery are required to open long-range fire on the enemy’s columns and so to cause delay by deployment; and to concentrate upon them while in, or emerging from, a defile. Infantry and Machine-gun Platoons are required for prolonged fire-fights and local counter-attacks, during which sudden bursts of machine and Lewis-gun fire will do the greatest execution. Engineers provide sappers for the creation of obstacles and traps, and for the demolition of bridges and viaducts. Mechanical Transport may be required to add to the mobility of the infantry. The Medical Service is called upon to provide attention and ambulances for the wounded and for the sick and worn-out troops.
DISTRIBUTION.—The Rear Guard is divided into two parts—the Rear Party and the Main Guard. The Rear Party consists, like the Vanguard of the Advanced Guard, of patrols and supports; the rest of the force forms the Main Guard, and marches in the order in which the troops are required, viz.: Artillery (with escort), Mounted Troops (if any remain over from the Rear Party), Infantry, Medical Services and Ambulances, and the Sappers of the Royal Engineers. The guns can thus open fire whenever required, and the sappers, who are furthest away from the pursuit, will have the longer time to prepare obstacles and demolitions, the latter being completed by the Rear Party. Communication must always be secured and maintained between the Rear Party and the Main Guard, and between the Rear Guard and the Main Body.
DISTANCE.—The distance at which the Rear Guard works is governed by the duty it has to perform, viz.: to permit the withdrawal of the Main Body to be carried out without interruption by the enemy, and to effect this it will usually be necessary for the Machine Gun and Infantry Platoons of the Main Guard to keep within effective range of positions from which hostile artillery might molest the Main Body. The commander will probably remain with this part of his force, as its work is of the highest importance; in any case his position must be made known and there should be definite commanders of the Rear Party and the Main Guard. But while the distance separating the Rear Guard from the Main Body must be sufficient, it must not be too great, or the enemy may penetrate between it and the Main Body, and not only will the Rear Guard be cut off and liable to destruction but it will cease to protect the Main Body.
TACTICAL PRINCIPLES.—The tactical work of a Rear Guard is carried out according to the following principles:—
The Rear Party watches, and it must watch all the roads and tracks by which the pursuing force can advance, and is responsible that the enemy does not get round the flanks (which may or may not be specially protected by Flank Guards). Reconnaissance by Aircraft for the discovery of intended outflanking movements is probably of greater value in Rear Guard work than in any other military action. The Rear Party also resists the hostile advanced troops as long as possible, withdrawing before it is outflanked. “An outflanking manoeuvre is specially convenient when attacking a Rear Guard, for the latter cannot fulfil its mission once it has been turned” (Marshal Foch).
The Main Guard fights for time. If the withdrawal is more or less unmolested, or if such pursuit as is offered can be dealt with by the Rear Party, the Main Guard can continue its march, taking care not to close in on the Main Body; and while falling back it can demolish bridges, create obstacles, prepare ambushes, and so on, employing all devices (within the laws of war) for delaying the enemy. When hotly pursued it must gain time at all costs for the army it is covering, and must not allow itself to be driven back on to the Main Body; or it will hamper that force and cease to protect it. Time can be gained by compelling the enemy to halt to reconnoitre a position, by making him deploy into attack formation, and by making him go out of his way in order to envelop a flank. But before an attack reaches a position in such strength as to ensure success, and before the enveloping force can achieve its object, sub-divisions of the Main Guard will withdraw in succession under covering fire from those still in the line, which also withdraw in their turn under covering fire from the sub-divisions in their new positions, to tactical points further back, from which again they cover the withdrawal of the forces which had protected their own movement.
Certain points must be noted about the positions chosen for these successive fire-fights, and the choice of the positions is so difficult that an experienced staff officer should be specially detailed for the work, Positions chosen must be in the enemy’s way and the lines of withdrawal to them must not converge; they must be easy to defend and difficult to attack; the flanks must be secure from direct attack and effective enfilade fire, necessitating a wide detour (and consequent gain of time from the enemy) before they can be threatened; long-range artillery fire on the lines of approach should be possible in order to delay and break up the enemy’s advance; and each position chosen for the next line of resistance should be unseen by the pursuing enemy, and sufficiently far away from the line last occupied to induce him to resume his march formation. This will necessitate a repetition on the part of the enemy of all the stages of the attack—the discovery and the report on the position, the decision to attack, and the deployment into attack formation. It will often be of advantage for a Rear Guard to take up a delaying position one or two hours before dark, as the enemy will then have to attack with darkness approaching and may wish to defer the attack until daylight, thus gaining several hours for the protected force.
“The first position taken up by a Rear Guard after an unsuccessful fight must be held longer, as a rule, than the subsequent positions, because when once the defeated army has got well away along the roads and has regained some semblance of organisation, the march continues without interruption unless some obstacle has to be crossed” (General Haking, “Staff Rides”). It can also be noted that as it is seldom the intention of the Rear Guard commander to deliver a decisive counter-attack, he can detail a very large proportion of his force to hold the successive positions, with local reserves, for purely local counter-attacks; and for the same reason, an obstacle in front of his position (which would make that position unsuitable for the Active Defence, as it would prevent the advance of the General Reserve to the decisive counter-attack) is most welcome in the Delaying Action of a Rear Guard fighting for time for its Main Body.
When at length a line of resistance is evacuated, the heavy artillery will be withdrawn first to move to a distant fire position, then the slow moving infantry and the light artillery (under the protective fire of the aircraft and mobile troops), and last the cavalry and other mobile troops, who by reason of their superior mobility, can hang on to the last and can protect the flanks of the Rear Guard as they fall back, before resuming their work as a Rear Party, observing and resisting the advanced troops of the pursuing force.
During a close pursuit the Rear Guard commander will be called upon to exercise all his faculties and to exert all his tactical ability in handling his command. One of the most anxious times before him will be when the Main Body is passing through a defile, as such a passage will not only delay its march but will make its columns particularly vulnerable and helpless. In the case of defiles Napoleon’s maxim must be borne in mind: “It is contrary to the principles of war to let one’s parks and heavy artillery enter a defile if the other end is not held also.” At Sannah’s Post (March 31, 1900) the train was permitted to enter a defile caused by the banks of the Koorn River without the previous occupation of that defile, and all the wagons were captured. This not only emphasises the necessity for an Advanced Guard in retreat, but points to the need of tactical knowledge on the part of the Rear Guard commander, especially in mountainous country or in terrain cut up by woods and marshes, where the train is liable to cause delays, as the withdrawing force is compelled to march in a long drawn column. Extra time must be gained by the Main Guard to enable the Main Body to emerge from the defile. The Rear Guard commander must therefore adapt his plans to suit the country through which the Main Body has to pass, as well as the country in which he will himself fight Delaying Actions. A good map and ability to use it, and close co-operation with the Main Body, must be determining factors for success or failure.
TRAINING.—When troops are being exercised in Rear Guard work opportunities should be taken to explain the difficulties of choosing suitable positions, of withdrawing from them when involved in battle, of the paramount necessity for mutual support, and of accepting any risk that may be required to safeguard the Main Body. Stress should be laid upon the importance of Fire Tactics (the judicious combination of Fire and Movement), the greatest of all factors in a successful Rear Guard battle, and upon the ability to read and understand a map, an essential qualification in all movements of troops and indispensable in Rear Guard fighting. From the map a platoon commander must be able to predict the probable line of the enemy’s advance against the line of resistance as well as the best route to be taken when, at length, he withdraws his platoon to another fire position in rear; while he must be prepared to throw his platoon in local counter-attack on the flank or rear of an assaulting party that has become detached from its supports and therefore affords a fleeting opportunity for a local fighting success, and a rapid advance for this purpose along a route unseen to the foe, a speedy reorganisation after victory, and a rapid withdrawal to the point of issue, or to a line in rear, can best be achieved by use of the map and reconnaissance of the ground of the encounter.
EYE FOR GROUND.—One of the secrets of Napoleon’s extraordinary successes was his “eye for ground.” “It was not until I went to Jena and Austerlitz that I really grasped what an important part an eye for ground like Napoleon’s, or blindness as to ground like his opponent’s at both those battles, may play in Grand Tactics, that is, the art of generalship” (Colonel G. F. R. Henderson, “The Science of War”). The same was true of General R. E. Lee, particularly in the Wilderness Campaign, when it was not only the entrenchments but the natural features of the ground on which he relied in his defensive tactics. “His eye for ground must have been extraordinary. The campaign was fought over a very large area, an area of very close country, with few marked natural features; and yet in the midst of woods, jungles, and streams, with very little time at his disposal, he always seems to have selected positions than which none could have been stronger” (Colonel G. F. R. Henderson, “The Science of War”).
EXAMPLES OF REAR GUARD WORK.—During the Retreat from Mons the Rear Guard of the II. Corps of the British Expeditionary Force delayed the pursuit by the daring and devotion of its cavalry and artillery, and by subordinating its plans to the interests of the Main Body enabled the Corps Commander (General Sir H. Smith-Dorrien) not only to throw off the pursuit but to effect a junction with the other wing of the British Army. The retreat took place after the First Battle of Le Cateau (August 26, 1914), and during the period of the retreat the insecurity of the British Army through the breakdown of a co-operating force rendered it liable to disaster. But the moral of Marshal French and his commanders, the stubborn fighting instincts of the British race, and the excellence of the musketry training of the Regular Army in times of peace, prevented the retreat from becoming a rout. The care taken in training the troops in Fire Tactics, and particularly in reloading with “eyes on the mark and butts to the shoulder,” was most abundantly justified. The accuracy and volume of the rifle fire deceived the enemy as to the nature of the troops employed against them, and the dismounted troops and infantry with their rifles were reported as “battalions of machine gunners.”
During the Second Battle of the Somme (March, 1918), the British III, and V. Armies fought a series of Rear Guard battles, and the enemy’s advance was made at a very heavy cost. “Units retreated stubbornly from one position to another as they found them turned and threatened with isolation; but at many points fierce engagements were fought, and whenever the enemy attempted a frontal attack he was beaten off with loss” (Sir D. Haig’s Dispatches). The machine gun proved its effectiveness again and again during the British withdrawal, and twelve machine guns of the 63rd Division, posted in Les Boeufs (March 24, 1918), held up the enemy’s advance from Morval at a critical period, and enabled the division to reach the position assigned to it. The losses inflicted on the enemy by machine-gun and rifle and Lewis-gun bullets were so heavy that by March 25 Von Below’s XVII. Army was described in German dispatches as “quite exhausted.” During the same battle a detachment of about 100 officers and other ranks, under the command of the Brigade-Major of the 61st Brigade, held the enemy at bay from early morning until 6 p.m. at Le Quesnoy (March 27, 1918) and enabled the 20th Division to retire to its destined position.
At the Combat of Roliça (August 17, 1808) the French General Delaborde was outnumbered by the Anglo-Portuguese forces under Sir A. Wellesley, and being driven from his first and second positions he withdrew to the mountains. During his retreat “he brought every arm into action at the proper time... and retreated by alternative masses, protecting his movements by short, vigorous charges of cavalry... and he fell back, disputing the ground, to Quinta de Bugagliera” (Napier).
In December, 1808, and January, 1809, General Sir John Moore withdrew to Coruña before the armies of Napoleon (and when the Emperor returned to Madrid, before those of Marshal Soult). “He conducted his long and arduous retreat with sagacity, intelligence, and fortitude” (Napier), and it is interesting to note that as in the Retreat from Mons in 1914 and at the Second Battle of the Somme in 1918, so in the rear-guard actions which preceded the embarkation of Sir John Moore’s Army, the musketry of the British troops was the deciding factor: “the English muskets were all new, the ammunition fresh; and whether from the peculiar construction of the muskets, the physical strength and coolness of the men, or all combined, the English fire is the most destructive known” (Napier).
At Bristow Station (October 14, 1863) during General Meade’s campaign in Northern Virginia (after his defeat of General Lee at Gettysburg, July 1-3, 1863), a surprise attack by Stuart’s cavalry and infantry from General Rode’s Division caused the withdrawal of the Federal troops. General Warren covered the retirement and eventually withdrew his own forces unmolested after beating off several attacks with close-range musket fire.
Jean Victor Moreau, one of the greatest generals of the French Republic, became a general of division at the age of 33, and by his skill in extricating his forces from apparently certain disaster established in retreat a far greater reputation for generalship than his brilliant victories secured for him. In the spring of 1796 he defeated Latour at Rastatt and the Archduke Charles at Ettlingen, and drove the Austrians back to the Danube, but owing to the defeat and retreat of Jourdan he was compelled to regain the Rhine in a desperate and apparently hopeless effort. Yet he not only preserved his army intact but brought with him over 5,000 prisoners. In 1798 he again saved his army from destruction when hard pressed by the Russians and Austrians in Italy. Retreat was by no means his only or favourite manoeuvre, as he subsequently gained victory after victory over the Austrians in the campaign of 1800, drove them back behind the River Inn, and won the decisive victory of Hohenlinden (December 3, 1800), where the Austrians and their Bavarian allies lost 17,000 men and 74 guns against a total loss of 5,000 on the side of the French.